Method of producing high tensile strength steel strapping

ABSTRACT

A METHOD OF PRODUCING A HIGH TENSILE STRENGTH STEEL STRAPPING FROM A SEMI-KILLED STEEL, KILLED STEEL OR CAPPED STEEL. THE STEEL HAS A MANGANESE CONTENT IN THE RANGE OF FROM ABOUT 0.3% TO ABOUT 1% BY WEIGHT AND A CARBON CONTENT IN A RANGE OF FROM ABOUT 0.18% TO ABOUT 0.34% BY WEIGHT. THE STEEL IS HEATED ABOVE THE CRITICAL TEMPERATURE THEREOF AND HOT ROLLED TO A THICKNESS OF FROM ABOUT 250% TO ABOUT 400% GREATER THAN THE ULTIMATE DESIRED COLD ROLLED THICKNESS THEREOF AND THEREAFTER QUENCHED IN LAMINAR FLOW WATER TO A TEMPERATURE OF FROM ABOUT 550*F. TO ABOUT 750*F. THEREAFTER, THE QUENCHED HOT ROLLED STEEL IS COLD ROLLED TO A TICKNESS OF BETWEEN ABOUT 40% AND ABOUT 25% OF THE HOT ROLLED THICKNESS AND THEREAFTER SIMULTANEOUSLY CLEANED AND STRESS RELIEVED BY HEATING THE COLD ROLLED STEEL IN A PROTECTIVE ATMOSPHERE TO A TEMPERAUTRE IN THE RANGE OF FROM ABOUT 800*F. TO ABOUT 1050*F. FOR A TIME IN THE RANGE OF FROM ABOUT 5 SECONDS TO ABOUT 15 SECONDS.

United States Patent Oflice METHOD OF PRODUCING HIGH TENSILE STRENGTH STEEL STRAPPING Marion Paul Hunt, Chicago, and Alexander Buy, Palos Heights, Ill., assignors to Interlake, Inc., Chicago, Ill. No Drawing. Filed June 8, 1972, Ser. No. 261,006 Int. Cl. C21d 7/02, 7/ 14, 9/52 US. Cl. 148-12 39 Claims ABSTRACT OF THE DISCLOSURE A method of producing a high tensile strength steel strapping from a semi-killed steel, killed steel or capped steel. The steel has a manganese content in the range of from about 0.3% to about 1% by weight and a carbon content in a range of from about 0.18% to about 0.34% by Weight. The steel is heated above the critical temperature thereof and hot rolled to a thickness of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof and thereafter quenched in laminar flow water to a temperature of from about 550 F. to about 750 F. Thereafter, the quenched hot rolled steel is cold rolled to a thickness of between about 40% and about 25% of the hot rolled thickness and thereafter simultaneously cleaned and stress relieved by heating the cold rolled steel in a protective atmosphere to a temperature in the range of from about 800 F. to about 1050" F. for a time in the range of from about 5 seconds to about 15 seconds.

This invention relates to a method of producing high tensile strength steel strapping and more particularly to a method of producing a high tensile strength ductile steel strapping without extensive heat treatment after cold rolling.

'It is an important object of the present invention to provide a method of producing a high tensile strength, ductile steel strapping, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 1.0% by Weight and carbon present inv a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow water applied at ambient temperature for a time sufiicient to effect the temperature reduction thereof, cooling the quenched steel to ambient temperature to produce cooled and quenched hot rolled steel, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25 of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by heating the same in a protective atmosphere to a temperature in the range of from about 800 F. to about 1050 F. for a time in the range of from about seconds to about seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to amibent temperature, thereby to produce ductile, high tensile strength steel strapping.

Another object of the present invention is to provide a method of the type set forth wherein the cooled and 3,761,323 Patented Sept. 25, 1973 quenched hot rolled steel is cleaned by contacting the steel with a mild acid solution to remove the mill scale therefrom.

Another object of the present invention is to provide a method of the type set forth wherein the cold rolled steel is slit into a plurality of strips having a predetermined width and thereafter edge rolled to produce a cold rolled steel strapping.

Still another object of the present invention is to provide a method of the type set forth wherein the steel provided has a manganese content in the range of from about 0.3% to about 0.68% by weight.

Still another object of the present invention is to provide a method of the type set forth wherein the simultaneous cleaning and stress relieving of the cold rolled steel is accomplished by immersing the cold rolled steel in molten lead maintained at a temperature in the range of from about 900 F. to about 1000 F. for a time in the range of from about 5 seconds to about 15 seconds.

A further object of the present invention is to provide a method of producing a high tensile strength steel, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 1.0% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow water applied at ambient temperature for a time sufficient to effect the temperature reduction thereof, and cooling the quenched steel to ambient temperature, thereby to produce a steel having a high tensile strength.

A further object of the present invention is to provide a method of producing a high tensile strength steel wherein the manganese content is in the range of from about 0.3% to about 0.68% by weight and the hot rolled steel is quenched to a temperature in the range of from about 600 F. to about 700 F.

A still further object of the present invention is to provide a method of producing a high tensile strength, ductile steel strapping, comprising the steps of providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of about 0.3% to about 1.0% by weight and carbon present in a range of about 0.18% to about 0.34% by weight and heated above the critical temperature thereof and hot rolled to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof and quenched to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow water and thereafter cooled to ambient temperature, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness Within the thickness of the cold rolled steel is in the range of from about 40% to about 25 of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by heating the same in a protective atmosphere to a temperature in the range of from about 800 F. to about 1050" for a time in the range of from about 5 seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping tensile strength steel strapping.

A still further object of the present invention is to provide a method of producing a high tensile strength, ductile steel strapping as previously set forth wherein the cold rolled steel is slit into a plurality of strips having a desired width and thereafter edge rolled to produce a cold rolled steel strapping.

A still further object of the present invention is to provide a high tensile strength, ductile steel strapping wherein the manganese content is in the range of from about 0.3% to about 0.68% and the simultaneous cleaning and stress relieving thereof is accomplished by immersing the cold rolled steel in molten lead maintained at a temperature in the range of from aboht 900 F. to about 1000 F. for a time in the range of from about 5 seconds to about 15 seconds.

Heretofore, high tensile strength steel strapping commonly has been produced by treating carbon steel, having a carbon content of from about 0.45% by weight to about 0.55% by weight and a manganese content of from about 0.60% by weight of 0.90% by weight by cold reducing the steel to the desired gauge, slitting the cold reduced steel longitudinally into a plurality of strips of the desired width, feeding the cold reduced strips continuously into a furnace for heating the strips to a temperature above the critical range and passing the strips into a lead bath held at a predetermined temperature to promote the development of the final desired grain structure and physical characteristics as a result of isothermal transformation.

The disadvantages inherent in the above process were the expensive equipment necessary in order to heat-treat the steel strapping subsequent to the cold reduction thereof. Attempts have been made to remedy the above disadvantage such as those suggested in US. Pat. No. 3,311,- 512 granted Mar. 28, 1967 to August F. Mohri et al. and assigned to the Steel Company of Canada Ltd. The difiiculty with the process set forth in the above-identified patent is that a high manganese content steel is used, the manganese content being of from about 1.35% by weight to about 1.65% by weight. Another disadvantage is the requirement for an extensive process annealing of the cold reduced steel for about 6 hours. These two disadvantages are obviated by the process of the present invention.

We have found that the tensile strength and ductility requirements of a high strength steel strapping can be obtained by means of the present invention from a semikilled steel, a killed steel or a capped steel. The differences between the above enumerated steels is fully set forth in Engineering Metals and Their Alloys, by Carl H. Samans, published by the MacMillan Company, 1956 at pages 219 to 223, thereof.

The above objects of the present invention may be better understood by reference to the following examples:

EXAMPLE 1 A semi-killed steel having a carbon content of 0.25% by weight and a manganese content of 0.45 by weight was heated in the hot mill and finished at a temperature of 1550 'F. and hot rolled to reduce the thickness thereof. The steel was hot rolled to a thickness such that the cold rolled steel would be reduced by 66% of the hot rolled thickness. Specifically, the steel was hot rolled to a thickness of 294% greater than the ultimate desired cold rolled thickness and more specifically, the hot rolled steel was rolled to a thickness of about 0.59 inch.

The hot rolled steel was then transported to a laminar flow water quench wherein the hot rolled steel was contacted with a large volume of substantially laminar flow water applied at ambient temperature to cool the hot rolled steel to a temperature of 650 F. The hot rolled steel was contacted with the laminar flow water quench for about 10 seconds to efiect the temperature reduction.

After the hot rolled steel was quenched, it was air cooled to ambient temperature and thereafter immersed in a dilute acid bath to remove the mill scale which formed on the surface of the steel during the air cooling thereof. The acid bath was 12% sulfuric acid solution maintained at a temperature of about E, as is standard in the art.

After the steel was quenched and the mill scale removed therefrom, a cold rolling operation was employed further to reduce the thickness of the steel. A cold rolling lubricant was applied to the steel, and thereafter, the steel was cold rolled to a thickness of 0.20 inch. The cold rolled reduction of the thickness of the steel therefore was 66% or the thickness of the cold rolled steel was 34% of the thickness of the hot rolled steel. After the steel was cold rolled and while the steel had the lubricant thereon, it was slit into a plurality of strips or strapping, each of the plurality of strapping strips having a width of inch. The strapping was edge rolled to remove burrs and the like, and thereafter introduced into molten lead maintained at a temperature of 975 F. for about 10 seconds. The strapping, after it exited from the lead pot, had been cleaned of the lubricant and stress relieved, as will be apparent. The strapping was then cooled with water to a temperature below the flash point of the paint which was used to paint the strapping. After the strapping was painted and dried, it was coiled and stored prior to shiping.

P After the strapping was coln rolled and slit, it was tested for tensile strength and it was found to have a tensile strength of 143,700 p.s.i. The same strapping was tested after it was painted and found to have a tensile strength of 141,000 p.s.i. The ductility, as measured in percent of elongation for a 6 inch specimen went from 2.1% for the cold rolled strapping to 5.5% for the painted strapping.

These tests demonstrated that significant increases in the ductility of the strapping were provided without a significant loss in the tensile strength of the strapping. The immersion of the strapping in the molten lead provided both a stress relief function and also a cleaning function wherein the lubricant used for cold rolling was removed from the strapping. Additionally, as seen from the data set forth above, the ductility of the strapping was improved by over 250% with a sacrifice or very little in the tensile strength of the strapping.

EXAMPLE 2 A semi-killed steel having a carbon content of 0.18% by weight and a manganese content of 0.30% by weight was heated in the hot mill to a temperature of about 1650 F. and hot rolled to reduce the thickness thereof. The steel was hot rolled to a thickness such that the cold rolled steel would be reduced by 60% of the hot rolled thickness. Specifically, the steel was hot rolled to a thickness of 250% greater than the cold rolled thickness.

The hot rolled steel was then transported to a laminar flow water quench wherein the hot rolled steel was contacted with a large volume of substantially laminar flow water applied at ambient temperature to cool the hot rolled strip to a temperature of 550 F. The hot rolled steel was contacted with the laminar flow water for slightly more than 10 seconds to effect the temperature I reduction. After the hot rolled steel was quenched, it was air cooled to ambient temperature.and thereafter immersed in a dilute acid bath to remove the mill scale which formed on the surface of the steel during the air cooling thereof.

After the steel was quenched and the mill scale removed therefrom, the steel was cold rolled to reduce the thickness thereof. A lubricant was applied to the steel prior to the cold rolling operation. The cold rolled reduction was 60% or the thickness of the cold rolled steel was 40% of the thickness of the hot rolled steel. After the steel was cold rolled and while the steel had lubricant thereon, it was slit into a plurality of strips. The strips or strapping were edge rolled and thereafter introduced into molten lead maintained at a temperature of 800 F. for about 15 seconds. The strapping, after it exited from the lead pot had been cleaned of the lubricant and stress relieved. The strapping was then cooled with water to a temperature below the flash point of the paint used to paint the strapping. After the strapping was painted and dried, it was coiled and stored prior to shipping. t

' Subsequent to the cold rolling operation, the steel was tested for tensile strength-and found to have a tensile strength in excess of 151,000 p.s.i. and a percent elongation for a 6 inch specimen of about 1.3. Subsequent to the immersion in the lead pot, the strapping was again tested for tensile strength and found to have a tensile strength of about 148,000 p.s.i. and a percent elongation for a 6 inch specimen of about 4.5. The tests conducted demonstrated that significant increases of the ductility of the strapping were provided without a significant loss in the tensile strength of the strapping.

EXAMPLE 3 A semi-killed steel having a carbon content of 0.34% by weight and a manganese content of 1.0% by weight was heated in the hot mill to a temperature of about 1500 F. and hot rolled to reduce the thickness thereof. The steel was hot rolled to a thickness such that the cold-rolled steel would be reduced by 75% of the hot rolled thickness. Specifically, the steel was hot rolled to a thickness of 400% greater than the ultimate desired cold rolled thickness.

- The hot rolled steel was then transported to a laminar flow water quench wherein the hot rolled steel was contacted with a large volume of substantially laminar flow water applied at ambient temperature to cool the hot rolled steel .to a temperature of 750 F. The hot rolled steel was contacted with the laminar flow water quench for slightly less than 10 seconds to effect the temperature reduction. After the hot rolled steel was quenched, it was air cooled to ambient temperature and thereafter immersed in the dilute acid bath to remove the mill scale which formed on the surface of the steel during the air cooling thereof.

After the steel was quenched and the mill scale removed therefrom, a cold rolling operation was employed further to reduce the thickness of the steel. The steel was first lubricated and then cold rolled to a thickness of 25% of the thickness of the hot rolled steel. After the steel was cold rolled and while the steel had the lubricant thereon, it was slit into a plurality of strips. The strips or the strapping were edge rolled and introduced into a molten lead bath maintained at a temperatureof about 1050 F. for about 5 seconds. The strapping, after it exited from the lead pot, had been cleaned of the lubricant and stress relieved. The strapping was then cooled with water to a temperature below flash point of the paint which was used to paint the strapping. The strappingwas then painted and dried and coiled prior to shipping.

After the strapping was cold rolled and slit, it was tested for tensile strength and found to have a tensile strength of 165,200 p.s.i. The same strapping was tested after it was painted and found to have a tensile strength of 158,800 p.s.i. The percent elongation of the cold rolled steel for a 6 inch specimen was 1.6, whereas the percent elongation'for the specimen after it was painted was 5.6. It is clear that significant increases in ductility were ob tained without extensive sacrifice of tensile strength.

' Fully killed steel and capped steel were also used in lieu of the semi-killed steel of the examples, both the fully-killed and capped steel were satisfactory for the process of the presentinvention. Silicon may be present as a result of the killing process in a range of from about 0.01% by weight up to 0.4% by weight without adversely affecting the product produced by the process of the present invention. Silicon present in excess of about 0.4% by weight may cause the steel to be too brittle.

Steels having various manganese contents have been employed with the process of the present invention. Steels having manganese contents of about 0.3% by weight have been found satisfactory for the present invention. Also, steels having a manganese content of up to about 1.0% by weight have also been found satisfactory for the present invention. If the manganese content of the steel exceeds about 1.0% by weight, the cost of the steel becomes too great and the steel is somewhat sluggish in response to the process of the present invention. On the other hand, it is difficult to obtain steel having a manganese content of less than about 0.3% by Weight.

The carbon content of the steel may vary in the range of about 0.18% by weight to about 0.34% by weight, both AISI Grade 1020 and 1030 steels being acceptable for the process of the present invention. An explanation of the American Iron and Steel Institute (AISI) nomenclature is found on page 327 of Engineering Metals and Their Alloys.

The steel is heated in the hot mill to a temperature above the critical temperature thereof. The relationship between critical temperature and the carbon content of steel is set forth in the above-mentioned Engineering Metals and Their Alloys at page 373 thereof. Preferably, the steel is heated to a temperature of about 1650 F.; however, any temperature above the critical temperature thereof is satisfactory, provided that the steel is maintained above its critical temperature when it is hot rolled.

It is necessary, to hot roll the steel to a thickness of between about 250% to about 400% greater than the ultimate cold rolled thickness. That is, the hot rolled steel must have a thickness such that the cold rolled steel is reduced in the range of between about 60% to about 75%. Therefore, the cold rolled steel will have a thickness of between about 40% and about 25% of the hot rolled steel. If the hot rolled steel is too thin, then the cold reduction thereof will not produce the desired tensile strength. If the hot rolled steel is too thick, the extra cold reducing required to obtain the ultimate cold rolled thickness will not produce added tensile strength and will be wasted. Additionally, the final strapping will lose ductility and will be too brittle.

The laminar flow water quench is used to reduce the temperature of the hot rolled steel from above the critical temperature thereof to a temperature in the range of about 550 F. to about 750 F. in a time of about 10 seconds. Large quantities of water are used to effect this temperature reduction which is critical in the process. If the steel is quenched to a temperature of less than about 550 F., the steel becomes too brittle and also may wave or buckle. If the steel is quenched to a temperature above 750 F., the proper grain structure of well dispersed carbides which produce the required tensile strength is not obtained. The steel is preferably quenched to a temperature of 650 F.

Laminar flow quench is described in the British Journal of The Iron and Steel Institute, November 1962 in an article titled The Laminar Jet System for Cooling Hot Steel Strip by J. N. Adcock at page 909. The article shows the conditions necessary to provide rod-like jets of water which are substantially laminar flow jets that maintain the laminar characteristics thereof although disposed four to five feet above the steel strip. The laminar flow jet does not bounce off the steel strip as in prior art high pressure jet sprays nor does the laminar flow jet create a steam buffer at the metal surface. Instead, the laminar flow jet contacts the metal surface and gently flows outwardly along the surface of the metal to provide superior cooling characteristics to those obtained with a high pressure jet spray.

Laminar flow cooling is also described in the Iron and Steel Engineering Yearbook, 1967, in an article titled Hot Strip Mill Runout Table Temperature Control by P. M. Auman, et al. at page 678 and also in the Journals of Metals, August 1965, in an article titled Improved Steels through Hot Strip Mill Controlled Cooling by E. R. Morgan, et al. at page 829.

-In the present process, the steel strip exits from the hot mill at a temperature of about 1550 F. to about 1600 F. at a speed of about 1400 to about 1500 feet per minute. The distance from the last finishing stand in the hot strip mill to the first water header is 54 feet and the number of water headers used varies between six and twelve, depending on the initial temperature of the strip and the final desired temperature of the strip. The length that the strip travels underneath the water headers is from 54 feet to 190 feet, the length depending on the number of water headers used. The distance from the last water header to the coiler is 180 feet, which distance provides for air cooling of the strip after the water quench. The flow rate of the water used for each water header is 1500 gallons per minute in order to obtain a coiling temperature for the strip in the range of about 600 F. to about 800 F., the preferred coiling temperature being 650 F.

The steel, after the quenching thereof, is air cooled to the temperatures set forth above and/or to ambient temperature prior to coiling for storage or for further processing, which air cooling produces a substantial amount of mill scale on the surface of the quenched steel. This mill scale is cleaned by introducing the steel into a mild acid solution such as a 12% sulfuric acid which may be heated and maintained at a temperature of about 150 F. This cleaning or pickling step is well-known in the art.

After the mill scale has been cleaned, the steel is lubricated and cold rolled. A reduction in thickness of between 60% and 75% provides the required tensile strength for the strapping; a cold reduction of 65% is preferred. If the strapping is reduced in thickness less than about 60%, the required tensile strength is not imparted thereto. Whereas, if the strapping is reduced in thickness more than about 75 the extra work does not produce greater tensile strength and is wasted.

After the steel has been cold rolled and while the steel has the lubricant thereon, it is slit into strapping of desired widths and edge rolled, both processes being old in the art. The strapping still has the lubricant thereon and is simultaneously cleaned and stress relieved to remove the lubricant from the surface of the strapping, and at the same time to relieve the internal stress therein to produce a more ductile product. By heating the strapping to a temperature of between about 800 F. and 1050 F. for a time interval of from about seconds to 15 seconds in a protective atmosphere, the strapping is both stress relieved and cleaned Without losing too much tensile strength. In the examples given, the protective atmosphere was metallic lead which served to protect the strapping from oxygen while the strapping was at an elevated temperature, thereby preventing the formation of excessive amounts of mill scale thereon.

Flame heaters may also be used to heat the strapping wherein the flame reduces the amount of oxygen available to react with the heated metal strapping. It is intended that such a flame heater fall within the purview of the present invention. The strapping is preferably heated to a temperature of about 1000 F. for a time of about seconds, thereby to clean the lubricant from the surface of the strapping and to increase the ductility thereof by relieving the internal stress therein. If the strapping is heated to a temperature above 1050 F., the strapping will lose too much tensile strength. If the strapping is heated to a temperature less than about 800 F., there will not be enough ductility imparted thereto. The strapping is heated for a time interval of between about 5 seconds and about seconds to permit the strapping to reach the necessary temperature. Heating for longer periods of time is unnecessary and can be deleterious to the final product. Heating for shorter periods of time results in the strapping not being heated to the required temperature with a corresponding loss in the ductility imparted thereto.

Another significant advantage of the high tensile strength ductile steel strapping produced by the process of the present invention is the improved ductility with respect to bending. Heretofore, high tensile strength strapping produced by prior art processes such as those set forth above, might have adequate ductility with respect to elongation but not with respect to bending. The strapping produced by the present invention can be bent across the direction of cold rolling without breaking the strapping provided that there are two thicknesses of the strapping at the bend. This improved ductility with respect to bending is nowhere present in the prior art strapping which can only be bent if 9 or 10 thicknesses of strapping are provided at the bend. It is seen therefore that the process of the present invention provides a high tensile strength steel strapping which has not only ductility with respect to elongation but also with respect to bending. This feature is commercially important for many packaging uses in the industry and is not duplicated by prior art steel strapping.

After the strapping has been cleaned and stress relieved, it is cooled by a water quench to a temperature below the flash point of the paint used to paint the strap in order to prevent fires and industrial hazards. After the strapping has been so cooled, it is painted and is then ready to be coiled and thereafter shipped for sale.

While there has been provided what is at present considered to be the preferred embodiment of the present invention, it will be appreciated that certain alterations and modifications may be made herein without departing from the true spirit and scope of the invention, and it is intended to cover in the following claims all such alterations and modifications which fall within the true spirit and scope of the present invention.

What is claimed is:

1. A method of producing a high tensile strength, ductile steel strapping, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 1.0% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow water applied at ambient temperature for a time suflicient to effect the temperature reduction thereof, cooling the quenched steel to ambient temperature to produce cooled and quenched hot rolled steel, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25% of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by heating the same in a protective atmosphere to a temperature in the range of from about 800 F. to about 1050 F. for a time in the range of from about 5 seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature, thereby to produce ductile, high tensile strength steel strapping.

2. The method set forth in claim 1, wherein the steel provided is a semi-killed steel.

3. The method set forth in claim 1, wherein the steel provided has a manganese content in therange of from about 0.3% to about 0.68% by weight.

4. The method set forth in claim 1, wherein the steel is heated to a temperature of about 1600 F.

'5. The method set forth in claim 1, wherein the thickness of the heated steel is reduced by hot rolling the steel to a thickness in the range of from about 250% to about 333% greater than the ultimatedesired cold rolled thickness thereof.

, 6. The method set forth in claim 1, wherein the hot rolled steel is quenched to a temperature in the range of from about 600 F. to about 700 F.

7. The method set forth in claim 1, wherein the hot rolled steel is quenched with the laminar flow water for about 10 seconds.

8.- The method set forth in claim 1, wherein the quenched hot rolled steel is air cooled.

9. The method set forth in claim 1, wherein the cold rolled steel is simultaneously cleaned and stress relieved by heating the same in a protective atmosphere to a temperature in the range of from about 900 F. to about 1000 F. for a time in the range of from about seconds to about 15 seconds.

10. The method set forth in claim 1, wherein the cold rolled steel is simultaneously cleaned and stress relieved by heating the same in a protective atmosphere of liquid metal.

11.The method set forth in claim 1, wherein the cleaned and stress relieved cold rolled steel is-cooled by contacting the same with Water applied at ambient temperature.

12. A method of producing a high tensile strength, ductile steel strapping, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 1.0% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 550 F. to about 750. F. by cooling the hot rolled steel with laminar flow water'applied at ambient temperature for a time sufiicient to effect the temperature reduction thereof, cooling the quenched steel to ambient temperature to produce cooled andquenched hot rolled steel with mill scale thereon, cleaning the cooled and quenched steel by contacting the same with a mild acid solution to remove the mill scale therefrom, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25% of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by heating the same in a protective atmosphere to a temperature in the range of from about 800 F. to about 1050" F. for a time in the range of from about 5 seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature, thereby to produce ductile, high tensile strengthsteel strapping.

,13. The method'set forth in claim 12, wherein the mild acid solution is a dilute sulfuric acid.

' 14. The method set forth in claim 12, wherein the mild acid solution ,is a 12% sulfuric acid solution maintained atan elevated temperature.

L 15. A method of producing'a high tensile strength, ductile steelstrapping, comprising providing a steel selected from the group" consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 1.0% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow Water applied at ambient temperature for a time sufiicient to effect the temperature reduction thereof, cooling the quenched steel to ambient temperature to produce cooled and quenched hot rolled steel, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25 of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, slitting the cold rolled steel with lubricant thereon into a plurality of strips having a desired width and thereafter edge rolling the same to produce a cold rolled steel strapping with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel strapping with lubricant thereon by heating the same in a protective atmosphere to a temperature in the range of from about 800 F. to about 1050 F. for a time in the range of from about 5 seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature thereby to produce ductile, high tensile strength steel strapping.

16. The method set forth in claim 15, wherein the cold rolled steel is slit into strapping having a width in the range of from about inch to about 1 inch.

17. A method of producing a high tensile strength, ductile steel strapping, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 0.68% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 600 F. to about 700 F. by cooling the hot rolled steel with laminar flow water applied at ambient temperature for a time sufficient to effect the temperature reduction thereof, cooling the quenched steel to ambient temperature to produce cooled and quenched hot rolled steel, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25% of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by heating the same in a reducing atmosphere to a temperature in the range of from about 900 F. to about 1000 F. for a time in the range of from about 5 seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature, thereby to produce ductile, high tensile strength steel strapping.

18. A method of producing a high tensile strength, ductile steel strapping, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 1.0% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow water applied at ambient temperature for a time sufficient to effect the temperature reduction thereof, cooling the quenched steel to ambient temperature to produce cooled and quenched hot rolled steel, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25% of the thickness of hot rolled steel to produce cold rolled steel with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by immersing the same in molten lead maintained at a temperature in the range of from about 900 F. to about 1000 F. for a time in the range of from about seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature, thereby to produce ductile, high tensile strength steel strapping.

19. A method of producing a high tensile strength, ductile steel strapping, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 0.68% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thicknesses of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 600 F. to about 700 F. by cooling the hot rolled steel with laminar flow water applied at ambient temperature for a time sufiicient to effect the temperature reduction thereof, cooling the quenched steel to ambient temperature to produce cooled and quenched hot rolled steel with mill scale thereon, cleaning the cooled and quenched steel by contacting the same with a mild acid solution to remove the mill scale therefrom, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25% of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, slitting the cold rolled steel with lubricant thereon into a plurality of strips having a desired width and thereafter edge rolling the same to produce a cold rolled steel strapping with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by immersing the same in molten lead maintained at a temperature in the range of from about 900 F. to about 1000 F. for a time in the range of from about 5 seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature, thereby to produce ductile, high tensile strength steel strapping.

20. A method of producing a high tensile strength steel, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 1.0% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow water applied at ambient temperature for a time sufiicient to effect the temperature reduction thereof, and cooling the quenched steel to ambient temperature, thereby to produce a steel having a high tensile strength.

21. The method set forth in claim 20, wherein the steel provided for a semi-killed steel.

22. The method set forth in claim 20, wherein the steel provided as a manganese content in the range of from about 0.3% to about 0.68% by weight.

23. The method set forth in claim 20, wherein the steel is heated to a temperature of about 1600 F.

24. The method set forth in claim 20, wherein the thickness of the heated steel is reduced by hot rolling the steel to a thickness in the range of from about 250% to about 333% greater than the ultimate desired cold rolled thickness thereof.

25. The method set forth in claim 20, wherein the hot rolled steel is quenched to a temperature in the range of from about 600 F. to about 700 F.

26. The method set forth in claim 20, wherein the hot rolled steel is quenched with the laminar flow water for about 10 seconds.

27. The method set forth in claim 20, wherein the quenched hot rolled steel is air cooled.

28. A method of producing a high tensile strength steel, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 1.0% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow water applied at ambient temperature for a time sufficient to effect the temperature reduction thereof, cooling the quenched steel to ambient temperature to produce cooled and quenched hot rolled steel with mill scale thereon and cleaning the cooled and quenched steel by contacting the same with a mild acid solution to remove the mill scale therefrom, thereby to produce a steel having a high tensile strength.

29. The method set forth in claim 28, wherein the mild acid solution is a dilute sulfuric acid.

30. The method set forth in claim 28, wherein the mild acid solution is a 12% sulfuric acid solution maintained at an elevated temperature.

31. A method of producing a high tensile strength steel, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of from about 0.3% to about 0.68% by weight and carbon present in a range of from about 0.18% to about 0.34% by weight, heating the steel to a temperature above the critical temperature thereof, reducing the thickness of the heated steel by hot rolling the steel to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof to produce hot rolled steel, quenching the hot rolled steel to a temperature in the range of from about 600 to about 700 F. by cooling the hot rolled steel with laminar flow water applied at ambient temperature for a time sufiicient to effect the temperature reduction thereof, and cooling the quenched steel to ambient temperature, therey to produce a steel having a high tensile strength.

32. A method of producing a high tensile strength, ductile steel strapping, comprising providing a steel se lected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of about 0.3% to about 1.0% by weight and carbon present in a range of about 0.18% to about 0.34% by Weight, said steel having been heated above the critical temperature thereof and hot rolled to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof and quenched to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow water and thereafter cooled to ambient temperature, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25% of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by heating the same in a protective atmosphere to a temperature in the range of from about 800 F. to about 1050 F. for a time in the range of from about seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature, thereby to produce ductile, high tensile strength steel strapping.

33. The method set forth in claim 32, wherein the cold rolled steel is simultaneously cleaned and stress relieved by heating the same in a protective atmosphere to a temperature in the range of from about 900 F. to about 1000 F. for a time in the range of from about 5 seconds to about 15 seconds.

34. The method set forth in claim 32, wherein the cold rolled steel is simultaneously cleaned and stress relieved by heating the same in a protective atmosphere of liquid metal.

35. The method set forth in claim 32, wherein the cleaned and stress relieved cold rolled steel is cooled by contacting the same with water applied at ambient temperature.

36. A method of producing a high tensile strength, ductile steel strappi'ng, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of about 0.3% to about 0.68% by weight and carbon present in a range of about 0.18% to about 0.34% by weight, said steel having been heated above the critical temperature thereof and hot rolled to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof and quenched to a temperature in the range of from about 600 F. to about 700 F. by cooling the hot rolled steel with laminar flow water and thereafter cooled to ambient temperature, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25% of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by heating the same in a protective atmosphere to a temperature in the range of from about 900 F. to about 1000 F. for a time in the range of from about 5 seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature, thereby to produce ductile, high tensile strength steel strapping.

37. A method of producing a high tensile strength, ductile steel strapping, comprising providing a steel selected from the group consisting of semi-killed steel, ki le S eel and capped steel, the steel having manganese present in a range of about 0.3% to about 1.0% by weight and carbon present in a range of about 0.18% to about 0.34% by weight, said steel having been heated above the critical temperature thereof and hot rolled to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof and quenched to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow water and thereafter cooled to ambient temperature, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25% of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, slitting the cold rolled steel with lubricant thereon into a plurality of strips having a desired width and thereafter edge rolling the same to produce a cold rolled steel strapping with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant therein by heating the same in a protective atmosphere to a temperature in the range of from about 800 F. to about 1050 F. for a time in the range of from about 5 seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature, thereby to produce ductile, high tensile strength steel strapping.

38. The method set forth in claim 37, wherein the cold rolled steel is slit into strapping having a Width in the range of about inch to about 1 inch.

39. A method of producing a high tensile strength, ductile steel strapping, comprising providing a steel selected from the group consisting of semi-killed steel, killed steel and capped steel, the steel having manganese present in a range of about 0.3% to about 1.0% by weight and carbon present in a range of about 0.18% to about 0.34% by weight, said steel having been heated above the critical temperature thereof and hot rolled to a thickness in the range of from about 250% to about 400% greater than the ultimate desired cold rolled thickness thereof and quenched to a temperature in the range of from about 550 F. to about 750 F. by cooling the hot rolled steel with laminar flow Water and thereafter cooled to ambient temperature, reducing the thickness of the cooled and quenched hot rolled steel by cold rolling the steel to a predetermined thickness wherein the thickness of the cold rolled steel is in the range of from about 40% to about 25 of the thickness of the hot rolled steel to produce cold rolled steel with lubricant thereon, simultaneously cleaning and stress relieving the cold rolled steel with lubricant thereon by immersing the same in molten lead maintained at a temperature in the range of from about 900 F. to about 1000 F. for a time in the range of from about 5 seconds to about 15 seconds to remove the lubricant therefrom and to relieve the stresses therein to produce steel strapping, and cooling the steel strapping to ambient temperature, thereby to produce ductile, high tensile strength steel strapping.

References Cited UNITED STATES PATENTS 3,378,360 4/1968 McFarland 14812.4 3,513,036 5/1970 McFarland et al. 148:12.4 3,551,216 12/1970 Severing et a1. 148-12.1 3,615,909 10/1971 Grasshotf et a1 148l2.4

WAYLAND W. STALLARD, Primary Examiner U.S. c1. 14s12.1, 12.4 

